A heat-developable color light-sensitive material is known in the art. The heat-developable light-sensitive material and process therefor are described, for example, in Shashin Kogaku no Kiso (Principle of Photographic Engineering), Edition of Non-Silver Salt System Photography, Corona Co., pp. 242-255 (1982), and U.S. Pat. No. 4,500,626.
Furthermore, a method of forming a dye image by the coupling reaction of an oxidation product of a developing agent with a coupler is described in U.S. Pat. Nos. 3,761,270 and 4,021,240. Also, a method of forming a positive color image by the bleaching of a photosensitive silver dye is described in U.S. Pat. No. 4,235,957.
A method of releasing or forming imagewise a diffusible dye by a heat development and then transferring the diffusible dye to a dye-fixing image-receiving material has already been put into practice. In this method, both a negative dye image and a positive dye image can be obtained by varying the kind of the dye-donating compound used or the kind of the silver halide used. More specifically, this method is described in U.S. Pat. Nos. 4,500,626, 4,483,914, 4,503,137 and 4,559,290, JP-A-58-149046 (the term "JP-A" as used herein means an "unexamined published Japanese patent application"), JP-A-60-133449, JP-A-59-218443, JP-A-61-238056, EP-A-220746, JIII Journal of Technical Disclosure 87-6199 and EP-A-210660.
For obtaining a positive color image by a heat development, a large number of methods have been proposed. For example, U.S. Pat. No. 4,559,290 discloses a method of allowing a reducing agent or a precursor thereof to be present together with an oxidized DRR compound having no capability of releasing a dye image, oxidizing the reducing agent according to the amount of silver halide exposed by a heat development, and reducing the oxidized DDR compound with a reducing agent remaining unoxidized to release a non-diffusible dye. Furthermore, EP-A-220746 and JIII Journal of Technical Disclosure 87-6199 (Vol. 12, No. 22) disclose a heat-developable color light-sensitive material using a compound which releases a diffusible dye by the reductive cleavage of N--X bond (wherein X represents oxygen atom, nitrogen atom or sulfur atom) in the same mechanism as described above.
In these heat-developable light-sensitive materials, the matter of importance is how much the fogging can be suppressed at the heat development. Particularly, in the heat-developable light-sensitive material using a reductive dye-donating compound, the dye is released at the development, for example, by the oxidation reaction of the dissolved oxygen in the light-sensitive material and even when not exposed, the fogging disadvantageously increases.
In order to prevent this unnecessary oxygen oxidation, a method of adding a reducing agent to a light-sensitive material is described in JP-A-60-198540, JP-A-62-85241 and JP-A-62-201434. However, if such a compound is simply added to a layer containing light-sensitive silver halide, the silver halide is reduced to release a dye and the fog increases. Of course, even if the reducing agent is added to a layer adjacent to a light-sensitive layer, the fog is similarly some or less increased.
To solve this problem, a technique of adding a reducing agent to a layer in the outer side of a light-sensitive material farthest from the support and not adjacent to a light-sensitive layer is described in JP-A-5-127335 and JP-A-7-20620. This addition technique has a very high effect for preventing the increase of fogging, however, in the method described in JP-A-5-127335, it has been found that a certain particular smoke-like uneven density of image (unevenness like a black-and-white Japanese ink drawing very low in the density) is generated. Also, the technique described in JP-A-7-20620 where a countermeasure for the uneven density of image is taken account of has a problem that another uneven density of image is newly generated.